Merge pull request #322 from corngood/cygwin

Don't default to ucontext on cygwin.

Author: olk

include/boost/context/detail/config.hpp

@@ -30,10 +30,6 @@
 # define BOOST_CONTEXT_DECL
 #endif
 
-#if ! defined(BOOST_USE_UCONTEXT) && defined(__CYGWIN__)
-# define BOOST_USE_UCONTEXT
-#endif
-
 #if ! defined(BOOST_CONTEXT_SOURCE) && ! defined(BOOST_ALL_NO_LIB) && ! defined(BOOST_CONTEXT_NO_LIB)
 # define BOOST_LIB_NAME boost_context
 # if defined(BOOST_ALL_DYN_LINK) || defined(BOOST_CONTEXT_DYN_LINK)